Changeset findNext/Prev code doesn't cope with search errors well

The code in ActivityStreamHandler.searchFromChangeset() (https://extranet.atlassian.com/crucible/browse/FE-hg/src/java/com/atlassian/fisheye/activity/ActivityStreamHandler.java?r=48830dd#to870 - used by findPrev/Next only) copes very badly with search errors (resulting in this: https://extranet.atlassian.com/jira/browse/ADM-9656).

I'll add comments to describe what it's doing - it is really looking for the current changeset in the stream then finding the next one. it should never adjust it's start time (as then it will NEVER find it's current changeset), instead, widen its window and if it finds results beyond the time of the current changeset without finding the current changeset, it knows something is wrong (rather than iterating over EVERY changeset in that direction), like http://jira.atlassian.com/browse/CRUC-4097?focusedCommentId=208843&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-208843.